I did get very tired after Radiation finished and was very uncomfortable wearing a bra for 2-3 weeks afterwards. For me I would have needed a month to recover before being able to fully enjoy a holiday. I found I seemed to have a worse skin reaction after the radiation actually finished. I had had a mastectomy though which can mean a worse skin reaction.
Maybe you could book the holiday for a few weeks after radiation finishes so that you give yourself time to recover but don't get caught up in the day to day stuff and miss out. Hope you get to enjoy a wonderful holiday and celebrate the end of treatment with your family. Deanne xxx